• Title/Summary/Keyword: End Effector Platform

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Collision Avoidance Based on Null Space Projection for a Nonholonomic Mobile Manipulator (비홀로노믹 모바일 매니퓰레이터의 영공간 투영에 기반한 충돌 회피)

  • Kim, KyeJin;Yoon, InHwan;Song, Jae-Bok
    • The Journal of Korea Robotics Society
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    • v.17 no.1
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    • pp.32-39
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    • 2022
  • Since the mobile platform and the manipulator mounted on it move at the same time in a mobile manipulator, the risk of mutual collision increases. Most of the studies on collision avoidance of mobile manipulators cannot be applied to differential drive type mobile platforms or the end-effector tends to deviate from the desired trajectory for collision avoidance. In this study, a collision avoidance algorithm based on null space projection (CANS) that solves these two problems is proposed. To this end, a modified repulsive force that overcomes the non-holonomic constraints of a mobile platform is generated by adding a virtual repulsive force in the direction of its instantaneous velocity. And by converting this repulsive force into a repulsive velocity and applying it to the null space, the end-effector of the robot avoids a collision while moving along its original trajectory. The proposed CANS algorithm showed excellent performance through self-collision avoidance tests and door opening tests.

The Forward/Inverse Force Transmission Analyses of the Stewart Platform (스튜어트 플랫폼의 순방향/역방향 힘 전달 해석)

  • Kim, Han-Sung;Choi, Yong-Je
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.5 s.98
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    • pp.200-208
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    • 1999
  • The statics relation of the Stewart platform has been investigated from the viewpoint of the forward and inverse force transmission analyses. Two eigenvalue problems corresponding to the forward and inverse force transmission analyses have been formulated. The forward force transmission analysis is to determine the ranges of the magnitudes of the force and moment generated at the end-effector for the given magnitude of linear actuator forces. In reverse order, the inverse force transmission analysis is to find the range of the magnitude of actuator forces for the given ranges of the magnitudes of the force and moment at the end-effector. The inverse force transmission analysis is important since it can provide a designer with a valuable information about how to choose the linear actuators. It has been proved that two eigenvalue problems have a reciprocal relation, which implies that solving either of the eigenvalue problems may complete the forward/inverse force transmission analysis. A numerical example has been also presented.

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Force Transmission Analyses with Dimensionally Homogeneous Jacobian Matrices for Parallel Manipulators

  • Kim, Sung-Gaun;Jeha Ryu
    • Journal of Mechanical Science and Technology
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    • v.18 no.5
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    • pp.780-788
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    • 2004
  • To avoid the unit inconsistency problem in the conventional Jacobian matrix, new formulation of a dimensionally homogeneous inverse Jacobian matrix for parallel manipulators with a planar mobile platform by using three end-effector points was presented (Kim and Ryu, 2003). This paper presents force relationships between joint forces and Cartesian forces at the three End-Effector points. The derived force relationships can then be used for analyses of the input/output force transmission. These analyses, forward and inverse force transmission analyses, depend on the singular values of the derived unit consistent Jacobian matrix. Using the proposed force relationship, a numerical example is presented for actuator size design of a 3-RRR planar parallel manipulator.

Inverse and Forward Force Transmission Analyses of Parallel Manipulators using Dimensionally Homogeneous Jacobian Matrices (유니트 일치된 자코비안 행렬을 이용한 병렬구조 로봇의 힘전달 해석)

  • Kim, Sung-Gaun;Ryu, Je-Ha
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.1500-1505
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    • 2003
  • In order to avoid the unit inconsistency problem in the conventional Jacobian matrix, previously we presented new formulation of a dimensionally homogeneous inverse Jacobian matrix for parallel manipulators with a planar mobile platform by using three end-effector points based on the velocity relationship [1]. This paper presents force relationships between joint forces and Cartesian forces at the three End-Effector points. The derived force relationships can then be used for analyses of the input/output force transmission. These analyses, forward and inverse force transmission analyses, depend on the singular values of the derived dimensionally homogeneous Jacobian matrix. Using the proposed force relationship, a numerical example is presented for actuator size design of a 3-RRR planar parallel manipulator.

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Decentralized Motion Control of Mobile Manipulator

  • Phan, Tan-Tung;Suh, Jin-Ho;Kim, Sang-Bong
    • 제어로봇시스템학회:학술대회논문집
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    • 2003.10a
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    • pp.1841-1846
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    • 2003
  • The mobile platform-manipulator discussed in this paper is a three link manipulator mounted on a mobile platform. This mobile manipulator is used for welding operation and it is able to operate in a narrow space. The task of the torch, which is mounted at the end effector of the manipulator, is to track along the seam line and the task of the mobile platform is to move the origin point of the manipulator in order to go away from the singularity of the manipulator’s configuration. In this paper, the path planning for the motion of two subsystems (i.e., the manipulator and the mobile platform) was presented by the decentralized control method. Two controllers for the mobile platform and the manipulator were designed, and the relationship between the independent controllers is its state information. The simulation results are also presented to demonstrate the effectiveness of the control method.

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Design of the Parallel Manipulator for Minimizing the Extreme Articular Force in the Specific Translation Trajectory (특정 병진작업경로에서 최소의 관절힘을 받는 병렬형 매니퓰레이터의 설계)

  • 양현익;이종우;허원혁
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.13 no.3
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    • pp.68-75
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    • 2004
  • Recently, need of the parallel manipulator requiring superior precision is increasing for medical application and precision manufacturing. In this study, we convert a given complex translation trajectory of the moving platform into a set of segments and hence a complex motion of the moving platform can be tractable and easily controled in a very limited workspace. In addition force exerted. to each link is minimized so that the minimized force can be transmitted to the end effector of the moving platform. An user friendly program is developed to design Gough-type 6DOF parallel manupulator based on the proposed method.

Study on Manipulability of a Stewart Platform (스튜엇트 플랫폼의 조작성 연구)

  • 김한성;최용제
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1994.10a
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    • pp.901-906
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    • 1994
  • In designing and evaluating manipulators, itis important to understand the capability of kinematic and static performances. Both workspace and manipulability can be considered as such performance measures. In general, the measure of manipulability is related to the kinematics for serial type manipulators. However.in case of parallel manipulators such as Stewart Platform, the manipulability can be interpreted as the static capability of transforming the input forces of actuators to the wrench of the end-effector. In this paper, the mathematical and physical meanings of manipulability suggested in some research works have been examined, and more meaningful measure of manipulability using the absolute minimum eigenvalues of J $^{T}$ .del. J has been suggested, which has been applied to a Stewart Platform in order to investigate the manipulability of this mechanism..

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A New Device and Procedure for Kinematic Calibration of Parallel Manipulators

  • Rauf, Abdul;Kim, Sung-Gaun;Ryu, Je-Ha
    • 제어로봇시스템학회:학술대회논문집
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    • 2003.10a
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    • pp.1615-1620
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    • 2003
  • Kinematic calibration is a process whereby the actual values of geometric parameters are estimated so as to minimize the error in absolute positioning. Measuring all components of Cartesian posture, particularly the orientation, can be difficult. With partial pose measurements, all parameters may not be identifiable. This paper proposes a new device that can identify all kinematic parameters with partial pose measurements. Study is performed for a six degree-of-freedom fully parallel Hexa Slide manipulator. The device, however, is general and can be used for other parallel manipulators. The proposed device consists of a link with U joints on both sides and is equipped with a rotary sensor and a biaxial inclinometer. When attached between the base and the mobile platform, the device restricts the end-effector's motion to five degree-of-freedom and can measure position of the end-effector and one of its rotations. Numerical analyses of the identification Jacobian reveal that all parameters are identifiable. Computer simulations show that the identification is robust for the errors in the initial guess and the measurement noise. Intrinsic inaccuracies of the device can significantly deteriorate the calibration results. A measurement procedure is proposed and formulations of cost functions are discussed to prevent propagation of the inaccuracies to the calibration results.

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Calibration of Parallel Manipulators using a New Measurement Device (새로운 측정장비를 이용한 병렬구조 로봇의 보정에 관한)

  • Rauf, Abdul;Kim, Sung-Gaun;Ryu, Je-Ha
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.1494-1499
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    • 2003
  • Kinematic calibration is a process whereby the actual values of geometric parameters are estimated so as to minimize the error in absolute positioning. Measuring all components of Cartesian posture, particularly the orientation, can be difficult. With partial pose measurements, all parameters may not be identifiable. This paper proposes a new device that can be used to identify all kinematic parameters with partial pose measurements. Study is performed for a six degree-of-freedom fully parallel Hexa Slide manipulator. The device, however, is general and can be used for other parallel manipulators. The proposed device consists of a link with U joints on both sides and is equipped with a rotary sensor and a biaxial inclinometer. When attached between the base and the mobile platform, the device restricts the end-effector's motion to five degree-of-freedom and can measure position of the end-effector and one of its rotations. Numerical analyses of the identification Jacobian reveal that all parameters are identifiable. Computer simulations show that the identification is robust for the errors in the initial guess and the measurement noise.

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The Design of Sliding Mode Controller with Sliding Perturbation Observer for a Robust Control of Stewart Platform Manipulator (스튜어트 플랫폼의 견실제어를 위한 슬라이딩 섭동 관측기를 갖는 슬라이딩 모드 제어기 개발)

  • You, Ki-Sung;Park, Min-Kyu;Lee, Min-Cheol
    • Journal of Institute of Control, Robotics and Systems
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    • v.8 no.8
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    • pp.639-648
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    • 2002
  • The stewart platform manipulator is a manipulator that has the closed-loop structure with an upper plate end-effector and a base frame. The stewart platform manipulator has the merit of high working accuracy and high stiffness compared with a serial manipulator. However, this is a complex structure, so controllability of the system is not so good. In this paper, we introduce a new robust motion control algorithm using partial state feedback for a class of nonlinear systems in the presence of modelling uncertainties and external disturbances. The major contribution of this work introduces the development and design of robust observer for the state and the perturbation, which is integrated into a variable structure controller(VSC) structure. The combination of controller/observer improves the control performance, because of the robust routine called sliding mode control with sliding perturbation observer(SMCSPO). Simulation and experiment are performed to apply to the manipulator. And their results show a high accuracy and a good performance.